Michael C. Horowitz is an Associate Professor of Political Science at the University of Pennsylvania and the author of the award-winning book, The Diffusion of Military Power. He has published widely in academic journals and mainstream media outlets on topics including the role of leaders in international politics, military innovation and the future of war, and forecasting. Professor Horowitz has worked at the Department of Defense, is a Term Member of the Council on Foreign Relations, and is a member of the International Institute for Strategic Studies. He received a PhD in Government from Harvard University and a BA in Political Science from Emory University, Atlanta. Allan C. Stam is Dean of Leadership and Public Policy at the Frank Batten School at the University of Virginia. His work on war outcomes, durations, and mediation has appeared in numerous political science journals. Several grants have supported his work, including four from the National Science Foundation. His books include Win, Lose, or Draw (1996), Democracies at War (2002), and The Behavioral Origins of War (2004). He is the recipient of the 2004 Karl Deutsch award, given annually by the International Studies Association to the scholar under the age of forty who has made the greatest contribution to the study of international politics. Cali M. Ellis previously worked at the RAND Corporation, the Homeland Security Directorate of the Michigan National Guard, and the Michigan Governor's Office. She is a member of the Edward A. Bouchet Graduate Honor Society, and her awards include the National Science Foundation IDEAS-IGERT Graduate Fellowship, the APSA Janet Box-Steffensmeier Award, the ProQuest Dissertation Writing Award, and a Distinguished Service Medal from the Michigan National Guard. Ellis has a BA in economics from Bates College, Maine and an MPP from the University of Michigan Gerald R. Ford School of Public Policy, and has published in International Interactions (2015), the Journal of Homeland Security and Emergency Management (2013), PS: Political Science and Politics (2012), and the Journal of Applied Security Research (2008).

• 1. How leaders matter; 2. Systematically evaluating leader risk; 3. Leader risk across geography and time; 4. The experiences that matter I: military, rebel, age, and education; 5. The experiences that matter II: childhood, family, and gender; 6. 'L'état c'est moi', … or is it?

'The authors deftly dissect a notoriously difficult problem at the intersection of political science, history and psychology: when do attributes of leaders shape decisions to use force? And they make a compelling case that, naysayers notwithstanding, personality matters.' Philip E. Tetlock, Annenberg University Professor, University of Pennsylvania